Prosthesis, a medical term originated from the Greek word for “addition”, is an artificial extension that replaces a missing body part. In the case of an endoprosthesis, an artificial device is placed inside the body to replace the missing bodily part. This medical procedure has been widely used in many different situations. For example, endoprosthesis can be used in rebuilding joints, such as artificial hips and artificial knees. For another example, endoprosthesis has been applied to patients whose bones were amputated, including rebuilding cancer patients' limbs by creating an endoprosthetic bone and adjacent joint to replace the cancerous one.
In situations such as hip and joint replacement, wherein the prosthesis is designed to be fit or inserted into a bone, the replacements are often fixed to bones by press fitting the prosthesis into the host bone, which has been filled with bone cement such as polymethylmethracylate (PMMA). Bone cement was first used in the 1950s. Since then, some modifications have been made and alternatives have been developed to the original PMMA cement. However, the general technique that uses bone cement for prosthesis has not changed significantly in over the past 40 years. The common method of preparing the bone is to ream the bone with a bone reamer, and then inject bone cement into the medullary canal, then the prosthesis replacement is placed into the bone. The bone cement provides for an immediate fixation, similar to filling a tooth cavity. This technique always results in a smooth bore cortical host bone.
These days, millions of procedures of this type are conducted all over the world every year. However, a major clinical problem with such a system of fixing the prosthesis implant lies in the ultimate loosening of the bone-cement interface overtime.
When the implant has loosened, the prosthesis may need revision or replacement. In such case, the bone cement must be fully removed, and the prosthesis previously implanted in the body is removed and replaced by a new prosthesis. Such replacement operations usually cause loss of healthy bone substances, and are often more complex and more difficult than the original prosthesis operation. In addition, prosthesis revision operations are often more expensive for patients.
It has been found that there is rarely a loosening in the junction between the prosthesis and the cement, that is, at the prosthetic-cement junction. On the other hand, the main mechanism of loosening is the development of a loose interface between the bone and the implanted bone cement (PMMA). This problem can be solved by preparing the bone through a different method, using the new bone rifling system disclosed herein.
In using the common technique of reaming, the reaming results in the remaining bone being essentially a smooth, cortical, bony tube, with smooth internal surface, regardless of how the cement is mixed or implanted. Thus, there is minimal interdigitation of the cement into the bone. In addition, any interdigitation of the cement that may occur weakens over time, and the prosthesis is thus disconnected from the interior surface of the bone, resulting in the need to surgically reset the prosthesis.
Accordingly, there is a need to provide a system which increases prosthetic bone fixation, reliably secures the prosthesis with respect to the bone, thereby eliminating the need to conduct further surgery as the bone-cement interface does not deteriorate over time. There is also a need to use the new system to prepare the host bone in prosthesis.